Capacitive sensor on duet WiFi 1.04 connecting



  • Does the Duet WiFi 1.04 with a capacitive Z-Probe sensor require an optocoupler module? The documentation states that you can just hook up the ground and signal wire as usual and then the power to VIN. Wouldn’t the signal be 24v (using 24v power) when high and thus require an optocoupler? Unless the Duet is taking the signal to a workable range for the board.


  • administrators

    If it's a Duet 1.04 then the Z probe input will tolerate 30V. However, you need to be very careful that you connect it to the correct pin on the Z probe connector. Recently a couple of users took the pinout from a Duet WiFi prototype wiring diagram that a Google search sometimes returns, and as a result they fed 24V into the 3.3V pin, which is disastrous. So when using a PNP-output sensor in particular, it's safest to use a couple of 10K resistors as a voltage divider on the output. See https://duet3d.dozuki.com/Wiki/Connecting_a_Z_probe?revisionid=HEAD#Section_PNP_output_normally_open_inductive_or_capacitive_sensor.



  • I decided to use a "1 Channel 24 V Board Protector Relay Module with Optocoupler High Support and Low Arduino Trip Level" board. I took the 5V from the "Always on Fan" for the common to send the signal to the board. Now if I just seeing it as always triggered. In the configurator I selected the Z-Probe Type Switch. The 5V being sent from relay is only on when probe is triggered. But board seems to think it is always triggered. Any ideas?


  • administrators

    Either add a pulldown resistor between the Z probe input and ground, or connect the relay contacts between the Z probe IN pin and ground instead of between IN and +5V.

    The 2-resistor connection is simpler.



  • As you saying remove the relay and just add a resistor to the signal cable which goes to Z_PROBE_IN. Just noticed that when triggered the voltage on the signal line of probe is .0003 and when not triggered it is 24V. It is suppose to be a NO. Figured it would be the opposite.
    How would I activate the signal on no voltage.



  • So I checked the relay wiring again and everything is wired correctly. It also switches and provides 5V on the output side when triggered. I removed the Z_PROBE_IN line and checked and it is showing 3.3V on that pin. Why is that? I thought this was an input pin.

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  • Also, Here is my Z-Probe config from the config.g

    ; Z-Probe
    M574 Z1 S2 ; Set endstops controlled by probe
    M558 P5 H5 F120 T6000 ; Set Z probe type to switch and the dive height + speeds
    G31 P500 X0 Y0 Z2.5 ; Set Z probe trigger value, offset and trigger height
    M557 X0:290 Y0:290 S20 ; Define mesh grid


  • administrators

    @twistedfab13 said in Capacitive sensor on duet WiFi 1.04 connecting:

    So I checked the relay wiring again and everything is wired correctly. It also switches and provides 5V on the output side when triggered. I removed the Z_PROBE_IN line and checked and it is showing 3.3V on that pin. Why is that? I thought this was an input pin.

    Depending on which Z probe mode you have selected in the M558 command in config./g, the internal pullup resistor may be enabled. That would explain the 3.3V reading. Mode 5 does enable the pullup resistor.

    The simplest fix is to rewire the relay output to connect the Z_PROBE_IN pin to ground instead of to +5V, and to add the i1 parameter to the M558 command.



  • That did it!! Thanks for you help.


 

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